HORIZONTAL OR WORKING PLAN.
This is the mining plan and guide, and whoever attempts to conduct an extensive mining operation without such a guide, or working plan, does injustice to himself or his employer.
This plan gives a "bird's-eye view" of the under-ground excavations, or such as could be seen in reality if the ground were removed from above the mine, or if it were trans parent and we could behold the numerous avenues and workings in the subterranean excavations. It portrays, on a miniature scale, all the gangways, headings, air-courses, tunnels, breasts, inclines, &c. &c., with the solid coal in advance, and the goaf, or exca vated portions, in the abandoned parts of the mine.
But in this horizontal view we only see the top or mouth of the shaft, which is repre sented on the paper as the area of the diameter. It gives no idea of the perpendicular height or depth of•shafts, slopes, inclines, or breasts. This can be obtained only from the transverse section. Nor would it represent the dip or underlay of the seam, which is also shown by the transverse section.
These plans are always drawn to a scale,—say from 20 to 100 feet to the inch; per haps from 30 to 50 feet to the inch may be the best scales for mining plans. If regular
scaled drawing-paper is not used, it is well to draw faint lines, two inches apart, at right angles across the paper, from north to south and from east to west. These are to remain and act as cardinal points, and serve as a base for protraction without bringing up north and south lines for that purpose. They also serve to indicate the course of levels, and act as proof of the surveys, as well as a guide to the plotter.
This plan, well constructed and proved, becomes invaluable to the manager. He has before him a complete miniature of the mine, and can tell at once where a tunnel may be driven, a slope put up to meet a descending one, a shaft started from the bottom or the top, and the best mode of drainage, ventilation, and general working is suggested or presented. He is not liable to get the mine in disorder or confusion by increasing or decreasing dips, and consequent changes in the strike of the seam, and course of the workings of the mine.